biostudies-literatureXu MNHLBI NIH HHS1546-57https://www.ebi.ac.uk/biostudies/studies/S-EPMC3327313biostudies-literatureUnknown23(8)Acid sphingomyelinase (ASM) mediates the formation of membrane raft (MR) redox signalosomes in a process that depends on a local acid microenvironment in coronary arterial endothelial cells (CAECs). However, it is not known how this local acid microenvironment is formed and maintained. The present study hypothesized that lysosomal V1 H(+)-ATPase provides a hospitable acid microenvironment for activation of ASM when lysosomes traffic and fuse into the cell membrane. Confocal microscopy showed that local pH change significantly affected MRs, with more fluorescent patches under low pH. Correspondingly, the ASM product, ceramide, increased locally in the cell membrane. Electron spin resonance assay showed that local pH increase significantly inhibited NADPH oxidase-mediated production of O(2)(Molecular biology of the cellRequirement of translocated lysosomal V1 H(+)-ATPase for activation of membrane acid sphingomyelinase and raft clustering in coronary endothelial cells.PMC3327313R01 HL075316R01 HL057244R01 HL091464R29 HL057244HL0765316HL057244HL091464Li PLZhang FRitter JKXu MHan WQXia MZhang YBoini KMLi XXfalseRequirement of translocated lysosomal V1 H(+)-ATPase for activation of membrane acid sphingomyelinase and raft clustering in coronary endothelial cells.Acid sphingomyelinase (ASM) mediates the formation of membrane raft (MR) redox signalosomes in a process that depends on a local acid microenvironment in coronary arterial endothelial cells (CAECs). However, it is not known how this local acid microenvironment is formed and maintained. The present study hypothesized that lysosomal V1 H(+)-ATPase provides a hospitable acid microenvironment for activation of ASM when lysosomes traffic and fuse into the cell membrane. Confocal microscopy showed that local pH change significantly affected MRs, with more fluorescent patches under low pH. Correspondingly, the ASM product, ceramide, increased locally in the cell membrane. Electron spin resonance assay showed that local pH increase significantly inhibited NADPH oxidase-mediated production of O(2)(2012-01-01T00:00:00Z2012 Apr2026-05-03T04:32:46.62Z2019-03-27T00:52:22ZS-EPMC33273132235761410.1091/mbc.E11-09-0821